Kefkas power is showcased in the exceptions, not the whole
My guess is that Amulet of Safekeeping is R&Ds attempt to try and answer the question of how to ensure that Modern players can sideboard against multiple strategies at once so that your progression though a large Modern tournament is less matchup dependent
Or, you know, you could splash out $20 and grab yourself Gisela, the Broken Blade, who costs one more mana, nearly doubles the Thunder Bird's stats, is a legendary, and has Lifelink while also being a flying creature with first strike
Remember the game plan of upsetting your opponents plan into a late-game win
Looking for Charmander prices and values
The difficulty with raw cards lies in the assessment of the condition of the card (i.e., how good of shape it is in) as that can be a fairly subjective assessment